Well, without knowing your exact CPU model number, I think it will be safe to say it is not supported.
However, that does not mean Windows 10 will not run on your PC.
If your graphics were provided by the CPU, they will likely not be supported as well.
Again, this does not mean you will not have graphics.
Now, upgrading to Windows 10 only works for Windows 7 and Windows 8.x. So, you will have to do a full install. And, any applications you had will have to be reinstalled. If you do not have your office install media, that is not necessarily a problem. If you do not, respond back with your office version.
Plus, there is always your data to back up and restore.
4GB memory is a little on the lean side, if you are going to install Windows 10 64-bit. But, it is not critical at this point.
Replacing the CPU a couple of years from now, in my opinion, really will not buy you much.
So, as a non-gamer, and using MS Office, you should be OK. I say that gently because, from an official standpoint, you will not be supported hardware-wise.
I recently upgraded over 20 machines, 15 of which were similar (to yours), and all upgraded successfully. Just saying.
Doc (all standard disclaimers apply)
This message was posted on behalf of Intel Corporation
At this point, I suggest you to take Al Hill advice, based on the information you provided your system does not support Windows® 10, you can still try to install Windows® 10 on your PC but how stable is going to be is hard to tell since there is no drivers available for your system.